Receding mechanism



Dec. 23, 1930.

G. M. PELToN RECEDING MECHANISM Fil-ed May 28, 192s new .,1 :sin

Patented Dec. 23, 1930 UNiTEDs-TATES PATENT oFFic GEORGE M. rnL'roN, CFMILWAU'KEE, WISCONSIN, AssIGNoR To THE FILER a s'roWELL COMPANY, or MILWAUKEE, .WIsCoNsIN, nl coRronArIoN or4 WISCONSIN RECEDING MECHn'NIsM Appncatin'iea May 2s, 192s. serial No. 231,170.`V

rlhis invention relates in general to saw-V mills and more particularly to mechanism for receding the knees of a sawmill carriagegy In general the object ofthe invention is to 5 provide a receding mechanism operable byv fluid pressure and acting at the proper time to effect an extremely rapid and powerful receding movement to the knee without subj ecting any of the parts to excessive stresses,

strains or shocks.

As is well known, in a sawmill the knees are slidably mounted on head blocks Xed to the carriage for movement transversely Vof the carriage and towardand away from the lsawl line. -The knees are advancedv toward the sawline by means of ak set shaft geared to the knees and appropriately driven under "the control of a setworks. The gearing betweeny the set shaft and the knee usually comprisesv 2c a pinion fixed to the set shaft and meshed with a rack carried by the underside of the knee and connected therewith. VVery frequently an adjustable connection is provided between the rack and the knee to permit of tapering movement of the knee.

The present invention starts with a sawmill of-this type and organizes a novel receding` mechanism therewith whereby the knees are quickly, powerfully and automatically reau ceded or'moved away from the sawline when desired. y A

in carryingout the present invention, a fluid pressure motor is mounted on the carriage and may consist of a cylinder fixed to the carriage and a piston operatively fitted in the cylinder. Positive motion transmission means between the piston and the knee constrains these parts to corresponding movement. 'Preferably this Vmotion transmission 4c means comprises a rack fixed to the piston and meshing with a pinion fixed to the set shaft. Means is provided for constantly maintaining pressure in the cylinder. vThe iiuid pressure acts on the piston to tend to cause the same torotate the set shaft reverselyK andthus recede the knee but when the set shaftiis drivenforward to advance the knee the piston moves against the action of the Huid pressure in the cylinder. When the sct shaftis released Vor disconnected from its drive the fiuid under pressure expands and moves the piston to rotate thei'set shaft reversely and to recede the knees. vIn other words, the advance vof the knees isyieldably resisted by the receding mechanism and at the proper time thereceding mechanism quickly and powerfully recedes the knee.

rlhe-rack connected with the piston of the receding mechanism preferably projects beyond an open end of its cylinder and into a combined rack housing and pressure chamber secured to the cylinder and communicating therewith on one side of the piston. .The fluid under pressure is supplied, preferably under substantially constant head, to this" combined i rack housing and pressurechamber;` lThe set' shaft traverses the vcombined rack housing and,V pressure-chamber and the portion of the set shaft'within the combined rack 'housing anjdpressure chamber carries the pinion that mesheswiththe rack. y

Suitable packing means is provided between the setshaft and the combined rackV housing 'andpressure chamber. Within the combined vrack housing 'and 4pressure chambermeans is provided Vfor guiding the rack and holding it in u mesh with its` pinion.

Other objects and advantages I reside in certain novel features ofthe construction, arrangement and combination ofparts which will be hereinafter more fully described and particularly pointed out in the appendedV claims, reference being had'to the" accompanying drawings forming a part of this specification, and in which:

' Figure 1 is a fragmentary plan view showing .the receding `mechanism applied to a portion of a sawmill carriage; V

Figure 2 `is a view partly in side elevationand partly in longitudinal vertical section vfurther illustrating the receding mechanismyof Figure 1 and showing diagrammatically a reservoir andl pump of any suitablefconstruction; Y.

Figures 3 and 4 are detail views in section taken on lines 3-3 and 4 4, respectively,l of Figure 1l; y Figure l5 is a diagrammatic perspective view illustrating how the knee and receding mechanism are associated with the and Figure 6 is a fragmentary detail view partly in elevation and partly in longitudinal vertical section illustrating how a valve controlled pipe line may be connected to the port at one end of the cylinder.

Referring to the drawings, the numeral 1 designates the side rails or side timbers of a. sawmill carriage which may be of any conventional construction. On this sawmill carriage a set shaft 2 is mounted in the usual manner and is geared to each knee 3 by a rack and pinion, as indicated diagrammatically at 4 in Figure 5. This construction as well as the means for driving and controlling the operation of the set shaft for advancing the knee toward the sawline are all well known in the art and need no detailed explanation here.

The present invention proposes a novel receding mechanism for reversely turning the set shaft 2 and thereby receding the knees. This receding mechanism comprises a cylinder 5 having integral lugs 6 bolted as at 7 to the sawmill carriage. The rearward end of the cylinder is closed by an endplate 8 and adjacent this rearward end the cylinder may be provided with a port which may be connected with a pressure supply but which ordinarily is equipped with a venting plug 9 having a restricted vent aperture. A piston 10 is fitted in the cylinder, the piston and the cylinder constituting a fluid pressure motor. One end of a rack 12 is secured as at 11 to the piston 10. The iack 12 projects beyond the inner open end of the cylinder 5 and into a combined rack housing and pressure chamber 13 having one end open and secured in pressure tight relation to the open end of the cylinder 5. This combined rack housing and pressure chamber 13 is also bolted to the carriage as indicated at 14. The set shaft 2 traverses or extends through the combined rack housing and pressure chamber 13 and the side walls of this combined rack housing and pressure chamber have stuffing boxes 15 for preventing any leakage of fluid pressure in between the set shaft and the opening through the side walls of the combined rack housing and pressure chamber. The portion of the set shaft 2 within the combined rack housing and pressure chamber has a pinion 16 fixed thereto and meshing with the rack 12. By means of the rack 12 and the pinion 16 the fluid pressure motor is positively geared to the set shaft. In other words, this rack 12 and pinion 16 constitute motion transmission means for constraining the piston 10 and the set shaft 2 and consequently also the knees to corresponding movement. The rack 12 is held in engagement with its pinion 16 by means of a roller 17 mounted for free rotation on a shaft 18 supported at set shaft;

its ends in openings provided therefor in the side walls of the combined rack housing and pressure chamber and held in position by tapered plugs 19 (see Figure fl). At spaced points in the combined rack housing and gear chamber 13, forwardly of the pinion 16, supporting rollers designated generally at 20 are provided. These supporting rollers are of spool-like construction having hubs 21 and end-plates or flanges 22 which engage lateral flanges 23 provided on the rack 12 (see Figure 3). Each supporting` roller 20 is mounted for free rotation on a pin 24 which has its ends received in sockets 25 provided in removable bearing plates 264 flanged to intert with and seal openings provided therefor in the side walls of the rack housing and pressure chamber and secured in position by stud bolts 27.

As shown in Figure 2, a pipe is connected to a passage 31 communicating with the pressure chamber 13. Preferably the pipe 30 is directly connected to some source of air er steam pressure having a substantially constant head. For example, an air reservoir like that shown diagrammatieally in Figure 2 at 32 may be used and the pressure in the reservoir may be maintained nearly constant by any well known form of pump and a pressure regulator. Pressure higher than atmospheric is thus maintained in the chamber 13 at all times during the operation of the sawmill. There. being no exhaust from the chamber 13 and the reservoir so connected, the system is a closed one and the pump connected to the reservoir makes up for any slight leakage around the piston or through the stuffing boxes 15. Movement of the piston 10 forwardly to the position of Figure 2 will increase the pressure in the chamber 13 and in the reservoir 32 and this increased pressure is used in quickly returning the piston when the works is released. It is to be understood, however, that in accordance with the preferred operation of the system pressure considerably greater than that produced by movement of the piston 1() is maintained in the chamber 13. This provides for quicker movement of the knee when the setworks is released than would be possible were only the piston 10 used to compress the air or other fluid in the chamber 13. It is obvious that if a relatively large reservoir is used, only a slight change in pressure will occur therein upon movement of the piston 10. The pressure in chamber 13 tends to 'force the piston 10 to the right as viewed in Figure 2, but when the knees are being advanced toward the sawline S, the set shaft 2 is positively driven or rotated by the usual means (not. shown) forwardly, that is, in a counter-clockwise direction, as viewed in Figure 2. This mot-ion of the set shafts acts through the pinion 16 and rack 12 to shift the piston 10 to the left, as viewed in Figure 2, notwithstanding the action of the fluid pressure. However, as soon as the set shaft 2 is released or disconnected from its driving or holding means the fluid under pressure immediately forces the piston 10 to the right as viewed in Figure 2 thereby rotating the set shaft reversely or in a clockwise direction, as viewed in Figure 2. This reverse rotation of the set shaft operates to recede the knees. During the rearward travel of the piston 10 the air in the cylinder 5 behind the piston is expelled throughthe restricted vent 9. This does not materially interfere with the receding motion during the major portion thereof but as the fluid in the pressure chamber and cylinder on the leftside of the piston, as viewed in Figure 2, expands the dierential between this pressure and the pressure existing on the right hand side of the piston is lessened. And so the final phases of the receding motion are carried out smoothly and without excessive impact thereby relieving the parts of excessive shocks and strains.

If desired, the port 9 may be connected through a valve controlled pipe line (see Figure 6) with a source offluid under pressure to permit the receding` means to be utilized to advance the knees forcibly and speedily vshould this be desired. In this connection it will be observed that if iuid pressure, such as compressed air, steam, or the like, is supplied to the right hand end of the cylinder 5 through the port 9 it will act on the right of the piston l0 and force the piston to the left as viewed in the drawings thereby so rotating the set shaft as to advance the knee. This dual action is made possible by virtue of the fact that the fluid pressure motor is in this respect at least double acting. f

The invention claimed is:

l. A receding mechanism for a knee of a sawmill carriage of the type wherein a set shaft is geared to the knee and turned in one direction for advancing the same and comprising a cylinder fixed to the sawmill carriage and having one end open, a piston operating in the cylinder, a rack fixed to the piston and projecting through the open end of the cylinder, a combined rack housing and pressure chamber connected to and communicating with the cylinder, and traversed by a portion of the set shaft, said housing extending and having a closed end beyond the end of the rack, a pinion fixed t-o the portion of the set shaft located in the combined rack housing and pressure chamber and meshed with the rack to turn the set shaft reversely when the piston is moved under the influence of fiuid pressure in the combined rack housing and pressure chamber and in the communicating end of the cylinder, and means for maintaining fluid pressure to the comhined rack housing and pressure chamber.

2. A receding mechanism for a knee of a sawmill carriage of the type wherein a set shaft is geared to the knee and turned in one direction for advancing the same and comprising a cylinder iixed to the sawmill carriage and having one end open, a piston operating in the cylinder, a rack fixed to the piston and projecting through the open end of the cylinder, combined rack housing and pressure chamber connectedto and communicating with the cylinder and traversed by a portion of the set shaft, said housing extending and having a closed end beyond the end of the rack, a pinion fixed to the portion of the set shaft located in the combined rack housing and pressure chamber and meshed with the rack to turn the set shaft reversely when the piston is moved under the iniuence of fluid pressure in the combined rack housing and pressure chamber and in the communicating end of the cylinder, means in said combined rack housing and pressure chamber for guiding the rack and holding it in mesh with its pinion, and means for maintaining fluid pressure to the combined rack housing and pressure chamber. A v

3. A receding mechanism for a knee of a sawmill carriage of the type wherein a set shaft is geared to the knee and turned in one direction for advancing the same and comprising a cylinder fixed to the sawmill carriage and having an open end, a piston operating in the cylinder, a flanged rack fixed to the piston and projecting beyond the open end of the cylinder, a combined rack housing and pressure chamber connected to and communicating with the cylinder and traversed by a portion of the set shaft, said housing extending and having a closed end beyond the end of the rack, a pinion fixed to the portion of the set shaft located in the combined rack housing and pressure chamber and meshed with the rack, a holding down roller sup-- ported to the pinion and engaging the back of the rack, spaced supporting rollers within the combined rack housing and pressure chamber having portions engageable with the flanges of the rack and means for maintaining fluid pressure to the combined rack housing and pressure chamber therewith.

4. The combination with a knee and a shaft for setting the knee of a sawmill, of a cylinder, a piston therein, a rack mounted directly on the piston, a pinion secured to the set shaft and engaging the rack to be driven thereby and an air tight housing for said rack and pinion secured to the end of the cylinder for forming a compression chamber on one side of said piston.

5. Means for driving the set shaft of a sawmill including a cylinder, a piston in the L cylinder, a rack secured directly to the piston, a pinion secured tothe set shaft and cooperating with the rack to he driven thereby, an air tight housing for the rack and pinion secured to the cylinder for forming a SOI compression chamber on one side of said piscon and means for admitting a Huid under pressure to said compression chamber.

6. The combination with a knee and a. shaft for setting the knee of a sawmill, of a cylinder, av piston therein, mechanical m0- t'on transmission means Connecting said piston an( seid shaft, and an air tight housing for said ineens for forming a compression Chamber on one side of said piston.

In Witness whereof, hereto aix my signa ture.

GEORGE M. PELTON` 

